Don't create nested types (or field accessors) for map types.

I'm sure I've implemented this before, but somehow it's been lost in a maze of twisty little branches, all alike.

csharp/src/ProtocolBuffers/WellKnownTypes/Struct.cs

@@ -16,7 +16,6 @@ namespace Google.Protobuf.WellKnownTypes {
 
       #region Static variables
       internal static pbr::FieldAccessorTable internal__static_google_protobuf_Struct__FieldAccessorTable;
-      internal static pbr::FieldAccessorTable internal__static_google_protobuf_Struct_FieldsEntry__FieldAccessorTable;
       internal static pbr::FieldAccessorTable internal__static_google_protobuf_Value__FieldAccessorTable;
       internal static pbr::FieldAccessorTable internal__static_google_protobuf_ListValue__FieldAccessorTable;
       #endregion
@@ -49,9 +48,6 @@ namespace Google.Protobuf.WellKnownTypes {
         internal__static_google_protobuf_Struct__FieldAccessorTable = 
             new pbr::FieldAccessorTable(typeof(global::Google.Protobuf.WellKnownTypes.Struct), descriptor.MessageTypes[0],
                 new string[] { "Fields", }, new string[] { });
-        internal__static_google_protobuf_Struct_FieldsEntry__FieldAccessorTable = 
-            new pbr::FieldAccessorTable(typeof(global::Google.Protobuf.WellKnownTypes.Struct.Types.FieldsEntry), descriptor.MessageTypes[0].NestedTypes[0],
-                new string[] { "Key", "Value", }, new string[] { });
         internal__static_google_protobuf_Value__FieldAccessorTable = 
             new pbr::FieldAccessorTable(typeof(global::Google.Protobuf.WellKnownTypes.Value), descriptor.MessageTypes[1],
                 new string[] { "NullValue", "NumberValue", "StringValue", "BoolValue", "StructValue", "ListValue", }, new string[] { "Kind", });
@@ -180,165 +176,6 @@ namespace Google.Protobuf.WellKnownTypes {
       }
     }
 
-    #region Nested types
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
-    public static partial class Types {
-      [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
-      public sealed partial class FieldsEntry : pb::IMessage<FieldsEntry> {
-        private static readonly pb::MessageParser<FieldsEntry> _parser = new pb::MessageParser<FieldsEntry>(() => new FieldsEntry());
-        public static pb::MessageParser<FieldsEntry> Parser { get { return _parser; } }
-
-        private static readonly string[] _fieldNames = new string[] { "key", "value" };
-        private static readonly uint[] _fieldTags = new uint[] { 10, 18 };
-        public static pbr::MessageDescriptor Descriptor {
-          get { return global::Google.Protobuf.WellKnownTypes.Struct.Descriptor.NestedTypes[0]; }
-        }
-
-        pbr::FieldAccessorTable pb::IReflectedMessage.Fields {
-          get { return global::Google.Protobuf.WellKnownTypes.Proto.Struct.internal__static_google_protobuf_Struct_FieldsEntry__FieldAccessorTable; }
-        }
-
-        private bool _frozen = false;
-        public bool IsFrozen { get { return _frozen; } }
-
-        public FieldsEntry() {
-          OnConstruction();
-        }
-
-        partial void OnConstruction();
-
-        public FieldsEntry(FieldsEntry other) : this() {
-          key_ = other.key_;
-          Value = other.value_ != null ? other.Value.Clone() : null;
-        }
-
-        public FieldsEntry Clone() {
-          return new FieldsEntry(this);
-        }
-
-        public void Freeze() {
-          if (IsFrozen) {
-            return;
-          }
-          _frozen = true;
-          if (value_ != null) Value.Freeze();
-        }
-
-        public const int KeyFieldNumber = 1;
-        private string key_ = "";
-        public string Key {
-          get { return key_; }
-          set {
-            pb::Freezable.CheckMutable(this);
-            key_ = value ?? "";
-          }
-        }
-
-        public const int ValueFieldNumber = 2;
-        private global::Google.Protobuf.WellKnownTypes.Value value_;
-        public global::Google.Protobuf.WellKnownTypes.Value Value {
-          get { return value_; }
-          set {
-            pb::Freezable.CheckMutable(this);
-            value_ = value;
-          }
-        }
-
-        public override bool Equals(object other) {
-          return Equals(other as FieldsEntry);
-        }
-
-        public bool Equals(FieldsEntry other) {
-          if (ReferenceEquals(other, null)) {
-            return false;
-          }
-          if (ReferenceEquals(other, this)) {
-            return true;
-          }
-          if (Key != other.Key) return false;
-          if (!object.Equals(Value, other.Value)) return false;
-          return true;
-        }
-
-        public override int GetHashCode() {
-          int hash = 1;
-          if (Key.Length != 0) hash ^= Key.GetHashCode();
-          if (value_ != null) hash ^= Value.GetHashCode();
-          return hash;
-        }
-
-        public override string ToString() {
-          return pb::JsonFormatter.Default.Format(this);
-        }
-
-        public void WriteTo(pb::CodedOutputStream output) {
-          if (Key.Length != 0) {
-            output.WriteRawTag(10);
-            output.WriteString(Key);
-          }
-          if (value_ != null) {
-            output.WriteRawTag(18);
-            output.WriteMessage(Value);
-          }
-        }
-
-        public int CalculateSize() {
-          int size = 0;
-          if (Key.Length != 0) {
-            size += 1 + pb::CodedOutputStream.ComputeStringSize(Key);
-          }
-          if (value_ != null) {
-            size += 1 + pb::CodedOutputStream.ComputeMessageSize(Value);
-          }
-          return size;
-        }
-
-        public void MergeFrom(FieldsEntry other) {
-          if (other == null) {
-            return;
-          }
-          if (other.Key.Length != 0) {
-            Key = other.Key;
-          }
-          if (other.value_ != null) {
-            if (value_ == null) {
-              value_ = new global::Google.Protobuf.WellKnownTypes.Value();
-            }
-            Value.MergeFrom(other.Value);
-          }
-        }
-
-        public void MergeFrom(pb::CodedInputStream input) {
-          uint tag;
-          while (input.ReadTag(out tag)) {
-            switch(tag) {
-              case 0:
-                throw pb::InvalidProtocolBufferException.InvalidTag();
-              default:
-                if (pb::WireFormat.IsEndGroupTag(tag)) {
-                  return;
-                }
-                break;
-              case 10: {
-                Key = input.ReadString();
-                break;
-              }
-              case 18: {
-                if (value_ == null) {
-                  value_ = new global::Google.Protobuf.WellKnownTypes.Value();
-                }
-                input.ReadMessage(value_);
-                break;
-              }
-            }
-          }
-        }
-
-      }
-
-    }
-    #endregion
-
   }
 
   [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]

src/google/protobuf/compiler/csharp/csharp_helpers.h

@@ -105,6 +105,12 @@ uint FixedMakeTag(const FieldDescriptor* descriptor);
 
 FieldGeneratorBase* CreateFieldGenerator(const FieldDescriptor* descriptor, int fieldOrdinal);
 
+// Determines whether the given message is a map entry message, i.e. one implicitly created
+// by protoc due to a map<key, value> field.
+inline bool IsMapEntryMessage(const Descriptor* descriptor) {
+  return descriptor->options().map_entry();
+}
+
 // Determines whether we're generating code for the proto representation of descriptors etc,
 // for use in the runtime. This is the only type which is allowed to use proto2 syntax,
 // and it generates internal classes.

src/google/protobuf/compiler/csharp/csharp_message.cc

@@ -121,6 +121,9 @@ void MessageGenerator::GenerateStaticVariables(io::Printer* printer) {
       "full_class_name", full_class_name());
 
   for (int i = 0; i < descriptor_->nested_type_count(); i++) {
+    // Don't generate accessor table fields for maps...
+    if (IsMapEntryMessage(descriptor_->nested_type(i))) continue;
+
     MessageGenerator messageGenerator(descriptor_->nested_type(i));
     messageGenerator.GenerateStaticVariables(printer);
   }
@@ -159,8 +162,10 @@ void MessageGenerator::GenerateStaticVariableInitializers(io::Printer* printer)
   }
   printer->Print("});\n");
 
-  // Generate static member initializers for all nested types.
+  // Generate static member initializers for all non-map-entry nested types.
   for (int i = 0; i < descriptor_->nested_type_count(); i++) {
+    if (IsMapEntryMessage(descriptor_->nested_type(i))) continue;
+
     MessageGenerator messageGenerator(descriptor_->nested_type(i));
     messageGenerator.GenerateStaticVariableInitializers(printer);
   }
@@ -285,7 +290,7 @@ void MessageGenerator::Generate(io::Printer* printer) {
   GenerateMergingMethods(printer);
 
   // Nested messages and enums
-  if (descriptor_->enum_type_count() + descriptor_->nested_type_count() > 0) {
+  if (HasNestedGeneratedTypes()) {
     printer->Print("#region Nested types\n"
 		   "[global::System.Diagnostics.DebuggerNonUserCodeAttribute()]\n");
     WriteGeneratedCodeAttributes(printer);
@@ -296,6 +301,9 @@ void MessageGenerator::Generate(io::Printer* printer) {
       enumGenerator.Generate(printer);
     }
     for (int i = 0; i < descriptor_->nested_type_count(); i++) {
+      // Don't generate nested types for maps...
+      if (IsMapEntryMessage(descriptor_->nested_type(i))) continue;
+
       MessageGenerator messageGenerator(descriptor_->nested_type(i));
       messageGenerator.Generate(printer);
     }
@@ -310,6 +318,21 @@ void MessageGenerator::Generate(io::Printer* printer) {
   printer->Print("\n");
 }
 
+// Helper to work out whether we need to generate a class to hold nested types/enums.
+// Only tricky because we don't want to generate map entry types.
+bool MessageGenerator::HasNestedGeneratedTypes()
+{
+  if (descriptor_->enum_type_count() > 0) {
+    return true;
+  }
+  for (int i = 0; i < descriptor_->nested_type_count(); i++) {
+    if (!IsMapEntryMessage(descriptor_->nested_type(i))) {
+      return true;
+    }
+  }
+  return false;
+}
+
 void MessageGenerator::GenerateCloningCode(io::Printer* printer) {
   map<string, string> vars;
   vars["class_name"] = class_name();

src/google/protobuf/compiler/csharp/csharp_message.h

@@ -69,6 +69,8 @@ class MessageGenerator : public SourceGeneratorBase {
   FieldGeneratorBase* CreateFieldGeneratorInternal(
       const FieldDescriptor* descriptor);
 
+  bool HasNestedGeneratedTypes();
+
   std::string class_name();
   std::string full_class_name();